1. Field of the Invention
This invention relates to a cartridge containing a disk, that is, a disk-shaped recording medium, on which predetermined information signals are recorded. More particularly, it relates to such a disk cartridge in which clamp means, including a magnetic plate adapted to be clamped by magnetic attraction to a disk table of the disk drive for rotating the disk, is provided in a disk cartridge half.
2. Description of the Prior Art
A known disk cartridge is so arranged as to keep therein a disk-shaped recording medium such as a so-called compact disk on the like in such a fashion that the disk-like recording medium can be reproduced in that state. This type of the disk cartridge is mounted in a recording and/or reproducing apparatus with the disk accommodated therein so that the information signals are written or recorded on and read from the disk. One half of the cartridge is provided with an opening through which the signal recording surface of the disk is exposed to the outside of the disk cartridge to be contacted by a recording and/or reproducing pickup device and opening through which a drive unit disk table is inserted to rotate the disk. The disk cartridge half is provided with a clamp unit in a facing relation to the opening into which the disk table is inserted, wherein the clamp unit operates to clamp the disk to the disk table in cooperation with the disk table. The clamp unit is adapted to clamp the disk under the force of magnetic attraction of a magnet provided in the disk table, and includes a clamper of synthetic material rotatably mounted to the inner lateral side of the disk cartridge half, and a magnetic plate secured to the clamper.
Such a known clamp unit is shown for example in FIGS. 1 and 2.
The clamp unit shown in FIGS. 1 and 2 includes a clamper 1 formed of synthetic material and a magnetic plate 2, such as an iron plate, attached to one major surface of the clamper 1. The clamper is substantially in a disk form and has a recess 3 at the center of one major surface thereof for accommodating the magnetic plate 2. On the bottom wall section 4 of the recess 3, there are formed three projections 6 adapted for engaging in three through-holes 5 formed in the magnetic plate 2. The magnetic plate is integrally mounted to the clamper 1 with the projections 6 engaged in the through-holes 5 and with the projections fused by the application of ultrasonic waves. The clamper 1 having the magnetic plate 2 attached thereto is rotatably mounted to a half 7 of the disk cartridge, as shown in FIG. 2. This half 7 is provided with a clamper attachment opening 8 into which the clamper 1 is introduced. The peripheral edge of the attachment opening 8 towards the inner side of the disk cartridge is formed with a retaining lug 10 directing towards the inside of the clamper attachment opening 8 for retaining a ring-like flange 9 projecting from the outer periphery of the clamper 1. The clamper is introduced into the attachment opening 8 with the flange 9 retained by the lug 10. The clamper 1 is prevented from the extricating from the attachment opening 8 by a cover plate 11 attached to the outer lateral surface of the half 7 for closing the attachment opening 8. The clamper is attached to the half 7 so as to be rotated freely within the gap between the cover plate 11 and the lug 10.
In the above described clamper system, an ultrasonic welding process is required, in which the projections 6 are fused for securing the magnetic plate 2 to the clamper 1 formed of synthetic material. Thus a mechanical system such as the ultrasonic welder is required with a complicated assembly process step. In addition, considerable investment costs are required for the mechanical system resulting in increased production costs.